Firing mechanism



United States Patent 2% Inventor fl- Lin 2.156.666 5/1939 Nardone 89/1 Madisomlll. 2.207.936 7/1940 Nardonenwi. i.......v...i 89/1 [21] A ppl.No. 779,156 3,399,479 9/1968 Goldstein 42/9 gg Primary Examiner-Verlin R. Pendegrass [73] Assign onncorporafion Attorneys-H. Samuel Kleser and William W. Jones a corporation of Virginia [54] FIRING MECHANISM ABSTRACT: A firing mechanism wherein a drum having a charge-receiving chamber is mounted for rotation in one D direction in a housing which has a loading port and a gas port. Chums 7 rawmg Figs A firing pin is provided in the drum and has a cam follower at- U.S. tached thereto The cam follower cooperates a am Cl. mounted on the housing to move the firing out of the {50] Field of Search .i 89/ 1.01, charge receiving chamber during rotation f the drum f 1142/9 the point where the charge-receiving chamber is in communication with the gas port to the point where it is in communica- [561 References cued tion with the loading port and to move the firing pin to a 9 3 9 3/ T B STIATES PATENTS cocked position and release it after the drum has been rotated l, 0 .07 19 3 oo son 89 1 360.

4 M 3v 4 4 14 j? a z m z My i 2 j l. 62 54 PATENTEU necze 19m sum 1 or 2 INVENTOR; CHAO H. L/N

Ly, $5 SMWZLM ATTORNEY FIRING MECHANISM This invention relates generally to firing mechanisms for actuating an explosive charge.

The particular firing mechanism of this invention is especially adapted for starting engines, such as small gasoline engines. Such engines are used to drive such apparatus as lawn mowers, outboard motors, chain saws, motorcycles and snowmobiles. To provide for the initial reciprocation of the piston and initial compression of the fuel charge to start the engine, some of these apparatuses are provided with an electrical starter. However, electrical starters are relatively expensive and thus, add to the cost of the apparatus. In addition, electrical starting can be relatively unreliable in extremely cold weather. In other cases, a hand crank is used for starting. However, this can be an extremely tiresome operation for the user in addition to being unreliable under certain circumstances.

The firing mechanism of the present invention utilizes the gas generated from the firing of a charge to provide for the initial reciprocation of the piston. A charge is placed in a charge receiving chamber and is mechanically actuated. The gas generated passes through an outlet which is in communication with the cylinder of the engine. The force of the gas on the piston in the engine cylinder causes the piston to reciprocate and start the firing cycle of the engine. By using gas generated from an explosive charge, the starting operation is not affected by weather conditions. In addition, the firing mechanism can be constructed relatively inexpensively, thus not adding substantially to the cost of the apparatus. Further, the firing mechanism of the present invention can utilize a caseless charge in the form of a pellet or the like, thereby eliminating the problem of extraction.

An object of the present invention is to provide an improved firing mechanism which can be usedto actuate an explosive charge.

A further object of the present invention is the provision of a firing mechanism which can be used for starting an engine.

Another object of the present invention is the provision of a firing mechanism having a continuous loading-ignition action.

A more specific object of the present invention is to provide a firing mechanism for firing an explosive charge which permits rapid loading and ignition of the charge.

A further object of the present invention is the provision of a firing mechanism which can utilize a caseless pellet of explosive powder.

Yet another object of the present invention is to provide a firing mechanism for use as an engine starter which is relatively inexpensive yet highly reliable.

These and other objects of the invention will become more readily apparent by reference to the following description of a preferred embodiment and also to the accompanying drawings in which:

FIG. I is a vertical, cross-sectional view of a preferred embodiment of a firing mechanism;

FIG. 2 is a horizontal, cross-sectional view taken along the lines 2-2 of FIG. 1;

FIG. 3 is a horizontal, sectional view taken along the lines 3-3 of FIG. 1 showing the relative position of the cam follower and the cam when the firing pin means is positioned as shown in FIG. 1;

FIG. 4 is a view similar to that of FIG. 3, but showing the cam follower in relation to the cam after the cam follower has been rotated clockwisely into loading position;

FIG. 5 is a vertical, cross-sectional view taken in the direction of the lines 5-5 of FIG. 4i

FIG. 6 is a view similar to that of FIG. 3, but showing the position of the cam follower relative to the cam with the mechanism positioned immediately prior to the firing operation; and I FIG. 7 is a vertical, cross-sectional view taken in the direction of the lines 7-7 of FIG. 6.

In general, the preferred embodiment of the firing mechanism of the present invention includes a housing 2 having an outlet 4 and a charge loading port 6. A rotatable drum 8 is mounted within the housing 2 and includes a charge receiving chamber 10 and firing pin means 12 for igniting a charge positioned within the charge receiving chamber 10. The bottom of the housing 2 is closed by a bottom cover plate 14 having a frustoconical raised portion 16 terminating in a flat upper surface 17 on which is mounted a cam 18 which controls the action of the firing pin means 12 as the drum 8 is rotated. A knob 20 is attached to the drum 8 to provide a means for rotating the drum 8.

More specifically, the housing 2 includes a generally cylindrical outer surface 22 from which the outlet 4 extends. The outlet 4 terminates in a reduced, threaded portion 24 which is adapted to be attached to an engine. The interior of the housing 2 includes a generally cylindrical bore 26 extending inwardly from the bottom thereof. The top of the housing is closed except for a cylindrical aperture 28 which extends therethrough and has an axis coincident with the axis of the bore 26. An enlarged support portion 30 extends on both sides of the top of the housing 2 in the area immediately surrounding the aperture 28. The outlet 4 has a bore 32 extending inwardly therein to a point short of the bore 26. A plurality of relatively small diameter bores 34 provide communication between the interior of the housing 2 and the bore 32.

The drum 8 is mounted within the bore 26 in the housing 2 and is in the form of a hollow cylinder having a diametrically extending rib 36 in the inside thereof. The outer wall 38 of the drum 8 is in sliding engagement with the wall of the bore 26 of the housing 2. A gas check groove 40 extends circumferentially about the outer wall 38 of the drum 8 adjacent each end thereof. Additional gas check grooves 42 are provided in the outer wall 38 in surrounding relationship to the charge receiving chamber 10.

The firing pin means 12 is mounted in a. horizontally extending bore 44 in the rib 36 of the drum 8. The bore 44 communicates with the charge receiving chamber 10. The firing pin means 12 includes a cylindrical body portion 46, a forward extension 48 having a tapered nose 50 adapted to contact the charge in the charge receiving chamber 10, and a rearward extension 52. The rearward portion of the bore 44 is closed by means of a threaded plug 54. Spring means 56 extend between the inner face of the plug 54 and the rearward face of the body 46 to bias the firing pin means 12 into its firing position. A shoulder 58 in the bore 44 provides a stop for abutment by the forward face of the body 46 to limit forward movement of the firing pin means 12. A cam follower 60 is attached to the firing pin means 12 and extends vertically through the body 46 thereof and also through an elongated opening 62 in the rib portion 36 of the drum 8 to a point below the bottom surface of the rib portion 36.

The bottom cover plate 14 is attached to the bottom of the housing 2 by any suitable means such as a plurality of screw members 64 and is so mounted that the frustoconical raised portion 16 extends inwardly toward the rib portion 36.0f the drum 8. The cam 18. including a cam surface 66 formed by its side edge, is mounted on the flat surface 17 on top of the frustoconical raised portion 16in a position wherein the cam follower 60 can engage the cam surface 66. The cam follower 60 is biased against the cam surface 66 by virtue of the spring means 56 urging the firing pin means 12in a direction toward the charge receiving chamber 10.

As shown in FIGS. 3-5, the cam surface 66 of cam 18 includes a first concavely arcuate portion 68 so positioned that when the cam follower 60 is in engagement therewith, the firing pin will be in its forwardmost position. In this position, the axis of the cam follower 60 is offset with respect to the axis of the bore 26 in the housing 2 in a direction away from the outlet 4. A second convexly arcuate portion 70 is provided on the cam 18 and is so shaped that its distance from the axis of the bore progressively increases. A third concavely arcuate portion 72 is provided immediately after portion 70 and is spaced from portion 68. A fourth'p'ortion 74 of the cam surface 66 is convexly arcuate and has its distance from the axis of the bore 26 progressively increasing. The final portion 76 of the cam surface 66 extends from the edge of portion 74 to the first portion 68 in a direction parallel to the axis between the loading port 6 and the bore 32 of the outlet 4 of the housing 2. The portion 76 is spaced from the axis a distance substantially equal to the radius of the cam follower 60.

A guide member 78 extends upwardly from the top surface 17 of the frustoconical portion 16 of the bottom cover plate l4 the same distance as the cam 18 and has an edge 80 parallel to cam'portion 76 and spaced therefrom a distance slightly greater than the diameter of the cam follower 60. The guide member 78 extends radially outwardly from the axis of the bore 26 in the housing 2a distance greater than cam surface 66.

The drum 8 includes a cylindrical extension portion 82 which extends through the aperture 28 in the top of the housing 2. The knob 20 is mounted on top of the housing 2 and includes a bore 84 which receives the extension portion 82. A dowel member 86 extends through a suitable opening in the knob 20 and extension portion 82 to provide a driving connection therebetween.

In the fired position of the mechanism, the components thereof are positioned as shown in FIGS. I3. The charge receiving chamber 10 is in communication with the small bores 34 in the housing 2 and the axis of the bore 44 containing the firing mechanism 12 is coaxial with the axis of the loading port 6 and the bore 32 in the outlet 4. In addition, the cam follower 60 is'positioned against the concavely arcuate portion 68 of the cam surface 66.

To load a charge into the charge receiving chamber 10, the knob is rotated 180 in a clockwise direction as viewed in FIGS. 35, whereupon a portion 70 of the cam surface 66 forces the cam follower 60 in a direction away from the charge receiving chamber 10 against the bias of the spring 56 until the cam follower 60 engages the concave arcuate portion 72 of the cam as shown in FIG. 4. At this point, as-shown in FIG. 5, the axis of the bore 44 containing the firing pin will have been rotated 180 until the charge receiving'chamber 10 is in alignment with the loading port 6. During this rotation, the cam 18 will have acted upon the cam follower 60 to move the forward portion 48 of the firing pin out of the charge receiving chamber 10 to permit the loading of a charge therein. By virtue of the concave arcuate portion 72 of the cam 18, the drum 8 will be releasably held in the loading position.

After a charge has been inserted into the charge receiving chamber 10, the knob 20 may be rotated in a clockwise direction to rotate the drum 8 until the cam follower 60 has reached the position shown in FIG. 6. At this point, the portion 74 of the cam surface 66 has acted upon the cam follower 60 to urge the firing pin means in a direction away from the charge receiving chamber 10 compressing the spring a predetermined amount to provide the necessary energy so that when the firing pin means is released, it will impact upon the charge in the charge receiving chamber 10 with enough energy to ignite the charge. Continued rotational movement of the knob 20 in the same direction will cause drum 8 to pivot about its axis until the cam follower 60 passes the end of the cam portion 72 and is aligned with the straight portion 76 in the position indicated by the dotted lines in FIG. 3. At this .point, the drum will have been rotated 360 from its initial fired position and the axis of the bore 44 will be coincident to the axis of thebore 32 and the loading port 6 with the charge receiving chamber 10 being in communication with the small bores 34. The cam follower 60 is now free to move along the cam portion 76 and the firing pin means 12 will be propelled forwardly under the influence of spring means 56 whereupon the firing pin means 12 will impact upon the charge in the charge receiving chamber 10, igniting the same, with the gases produced thereby passing through the bores 34 in the bore 32 in the outlet 4.

As the drum 8 is rotated the cam follower 60 will be in engagement with cam portion 74 until the drum 8 has been tional rotation of the drum 8 prior to the cam follower 60 and the firing pin means 12 moving into the fired position is prevented by guide member 78, which forms a'stop for the cam follower 60. thus insuring proper alignment'betweenthe charge receiving chamber 10 and the small bores 34. i

The provision of the shoulder 58 in the bore 44 which provides a stop face against which the forward face of the body 46 of the firing pin means I2 can impact and prevents undue shear from being applied to the cam follower 60 which would be the case if the cam follower were to impact upon the concave arcuate portion 68 of the cam surface. The concave arcuate portion 68 serves to releasably hold the drum 8 in the tired position.

I claim: 1. A firing mechanism comprising a housing including a gas port and a loading port, a drum mounted in said housing and rotatable about its axis, a charge receiving chamber in the outer wall-of said drum, said charge receiving chamber com municating with said gas port when said drum is in its firingfired position and communicating with said loading port when said drum is in a loading position. firing'pin means mounted in said drum, means biasing said firing pin means toward said charge receiving chamber, said firing pin means being movable in said drum between a fired position wherein a portion of said firing pin means extends into said charge receiving chamber and a firing position wherein said firing pin means is cocked in a direction against said bias, cam follower means at-' tached to and movable with said firing pin means, and cam means for engagement by said cam follower means for moving said firing pin means out of said charge receiving chamber as said drum is rotated in one direction from its firing-fired position to its loading position and also to move said firing'pin means into its firing position as said drum is rotated in said one direction and release said firing pin so it can move to its fired position after said drum is rotated 360 in said one direction.

2. The firing mechanism of claim I further including means for preventing rotation of said drum more than 360 in said one direction when said firing pin means is in said firing position. t

3. The firing mechanism of claim 2 wherein said cam means includes means for releasably retaining said drum in said loading position. I

' 4. The firing mechanism of claim 1 wherein said cam means includes means for releasably retaining said drum in said fired position.

5. A firing mechanism comprising a housing having a cylindrical bore therein, a drum having a cylindrical outer wall in sliding contact with said bore, a charge receiving chamber in said outer wall, a gas port in said housing communicating with the interior of said bore, aloading port extending through said housing and communicating with said bore, said drum being rotatable in one direction from a first firing-fired position wherein saidcharge receiving chamber is in communication drum, said bore communicating with said charge receiving chamber, means biasing said firing pin toward said charge receiving chamber, said firing pin being mounted in said bore for movement between a fired position wherein a portion of said firing pin extends into said charge receiving chamber and a firing position wherein said firing pin is cocked against said bias, a cam follower attached to and movable with said firing pin, a cam connected to said housing, said cam including cam surface means for engagement by said cam follower for moving said firing pin out of said charge receiving chamber as said drum is rotated in said one direction from its firing-fired position to its loading position and also to move said firing pin into its firing position as said drum is rotated in said one direction and release said firing pin so it can move to its fired position after said drum'is rotated 360in said one direction.

6. The firing mechanism of claim 5 wherein said cam surface means includes a first concavely arcuate portion for releasably holding said cam follower in a position wherein said drum is in its firing-fired position and said firing pin is in its fired position, a second convexly arcuate portion for engagement by said cam follower to move said firing pin out of said charge receiving chamber as said drum is rotated to said loading position, a third concavely arcuate portion for releasable engagement by said cam follower to releasably hold said drum in said loading position, a fourth convexly arcuate portion for engagement by said cam follower to move said firing pin to the firing position and a fourth straight portion for permitting release of said firing pin for movement from its firing to its fired position when said drum has been rotated 360.

7. The firing mechanism of claim 6 further including a stop member having a surface parallel to said fourth portion of said cam surface means and spaced therefrom a distance substantially equal to the thickness of said cam follower and being in a position to be engaged by said cam follower when said firing pin is in said firing position and said drum has been rotated 360 from said fired-firing position, said stop member being spaced from said cam surface means a distance at least as great as the thickness of said cam follower to permit move ment of said cam follower along said cam surface means.

8. The firing mechanism ofclaim 5 wherein said housing includes a top surface having a central aperture therein and said drum includes an extension portion extending through said aperture. and further including a knob member connected to said extension portion.

9, The firing mechanism of claim 5 wherein said bore extends into the bottom of the housing and further including a cover plate closing the bottom of said. housing. said cover including a dome portion extending inwardly and having an inner planar surface, said cam being mounted on said planar surface.

10. The firing mechanism of claim 5 wherein said loading port is circumferentially spaced 180 from said gas port. 

